Composite closures are well known in the prior art and have commonly been used for a wide variety of products which are cold filled, hot filled or thermally pasteurized or sterilized after filling and closing. Typically, these closures include a metal end panel which can be pre-lined with a suitable sealing material such as, for example, a plastisol gasket material and then inserted or pressed into a preformed plastic (e.g., polypropylene) fitment or shell. A tamper indicating band, typically formed of a plastic material, is commonly secured to the lower portion of the skirt.
Prior art closures of this general type have been described in a number of patents including, for example, U.S. Pat. Nos. 7,784,629 and 7,175,039 each of which describe closure caps having a plastic shell and a metal end panel or insert disk having a curl on the outer periphery that is received in a plastic shell or fitment wherein the curl at the outer periphery of the end panel is contacted by a plurality of fins or gussets angularly (obliquely) disposed with respect to the longitudinal access of the closure cap. These fins or gussets exert a positive downward force on the curl end panel during initial opening of the closure and deform upon contact with the curl.
Correspondingly, U.S. Pat. No. 6,662,958 describes a composite closure with a metal insert disk or end panel that is received in a plastic shell or fitment having a continuous bead or bead segments that extend downwardly from a lower surface of the ring (flange) of the plastic shell. A contact surface on the continuous bead or circumferentially disposed bead segments (e.g., gussets) extend downwardly from a lower surface of the ring (flange) of the cap shell. The contact surface of these beads, bead segments or gussets is non-parallel to the longitudinal axis of the closure cap and, as such, exert a downward force on the curl.
U.S. Pat. No. 4,880,127 describes a composite closure having a plastic shell and metal insert which utilizes a curved bead or projection in the shell to contact the lower portion of a curl of a metal insert disk and, as such, exerts a positive axial force onto the disk during initial opening of the closure.